A check valves is a device to control flow direction in fluid systems. By actuation mechanisms, they can be grouped into three categories: active valve is actuated by external forces; passive valve such as Domino valve is actuated by fluid motion; fixed-geometry or No-Moving-Part (NMP) valve does not require external power and has no moving mechanical parts or deformable structures, instead it allows easy passage of forward flow and discourages reverse flow utilizing fluidic force. The latter two types together are usually referred to as a fluid diode.
A fixed-geometry fluid diode with flat-walled structures (denoted as fluid diode hereinafter), i.e., a Tesla valve and diffuser. A Tesla valve is composed of a straight and an embowed channel, and it utilizes inertial effect to drive part of reverse flow to the embowed channel thus dissipates its energy. A diffuser is a flow channel with expanding cross-section, and no doubt that flow in this direction requires smaller driving pressure. The essential difference between Tesla valve and diffuser is the outlet/inlet width. FIGS. 1A and 1B illustrate exemplary fixed-geometry fluid diodes with flat walled structures.
A fixed-geometry diode cannot completely stop reverse flow, but they are advantageous due to easy fabrication, robustness, capability of handling particle-laden, multi-phase, oscillating flow. Therefore, they are widely employed in many varied applications. For instance an integrated Tesla valve into a flat-plate oscillating heat pipe to achieve circulatory flow, a constructed miniature valve-less membrane pumps using Tesla valve as fluidic rectifiers, and a diffuser is frequently used in fluid pumps. The original Tesla valve requires inflow and outflow ports to be specifically positioned and oriented. Fluid enters at the bottom the device with a large vertical component of velocity and exits on the side of the device with only horizontal components of velocity.
Accordingly, there is a need in the art for a fluid diode design that allows alignment of inlet and outlet ports and inflow and outflow to be in the same direction and allows for substantial improvement of the diodicity.